Molecular mechanisms underlying the retinal vascular lesions in diabetic retinopathy

血-视网膜屏障（BRB）在糖尿病视网膜病变中被破坏，从而加速疾病进程。然而，尽管组织缺氧被认为是糖尿病视网膜病变的触发因素，但尚未阐明BRB如何在糖尿病视网膜病变过程中发生破坏。在本研究中，BRB中断在糖尿病视网膜病变的机制进行了分析，参考视网膜组织缺氧，以及紧密连接的一个组成部分，在血管内皮细胞的表达。在体外，claudin-5从培养的融合脑源性内皮细胞（bEND.3）的细胞质到质膜的移动与跨内皮电阻（TEER）的增加密切相关，TEER是细胞单层屏障功能的指标。通过RNAi抑制claudin-5的表达导致TEER的降低，表明claudin-5在屏障保护中的关键作用。 ...更多信息 rty。低氧（1%O_2）改变了bEND.3细胞中claudin-5在质膜上的位置和claudin-5蛋白的水平，这些变化伴随着TEER的降低。在体内，claudin-5分子在常氧下在视网膜微血管内皮细胞的质膜中表达，但在缺氧条件下显著降低。示踪剂实验显示，具有抑制的claudin-5表达的缺氧视网膜血管系统的屏障功能针对小分子被选择性地破坏，这与claudin-5缺陷小鼠的表型非常相似。这些体外和体内数据表明，claudin-5是导致BRB破坏的缺氧的靶分子。此外，缺氧诱导的claudin-5表达的变化被证明在泛素-蛋白酶体途径的抑制剂MG-132的存在下被抑制，这表明泛素-蛋白酶体途径参与了缺氧诱导的BRB分解。少

Blood-retinal barrier (BRB) is known to be disrupted in diabetic retinopathy, which subsequently accelerates the progression of disease processes. However, it has not been clarified how the BRB breakdown occurs during the course of diabetic retinopathy, although the tissue hypoxia is thought to be involved as a trigger. In the present study, the mechanisms of BRB disruption in diabetic retinopathy were analyzed with reference to the retinal tissue hypoxia as well as the expression of claudin-5, a component of tight junctions, in vascular endothelial cells. In vitro, the movement of claudin-5 from the cytoplasm to the plasma membrane of cultured confluent brain-derived endothelial (bEND.3) cells was closely correlated with the increase in the transendothelial electrical resistance (TEER) which is an idex of barrier function of the cell monolayer. Inhibition of the expression of claudin-5 by RNAi resulted in a reduction of TEER indicating a critical role of claudin-5 in the barrier prope … More rty. Hypoxia (1% O_2) altered the location of claudin-5 in the plasma membrane and the level of claudin-5 protein in bEND.3 cells, and these changes were accompanied by a decrease in the TEER. In vivo, the claudin-5 molecules are expressed under normoxia in the plasma membrane of retinal microvascular endothelial cells, but were significantly reduced under hypoxic conditions. Tracer experiments revealed that the barrier function of hypoxic retinal vasculature with depressed claudin-5 expression was selectively disrupted against small molecules, which is very similar to the phenotype of claudin-5-deficient mice. These in vitro and in vivo data indicate that claudin-5 is a target molecule of hypoxia leading to the BRB disruption. Furthermore, the hypoxia-induced changes in claudin-5 expression were shown to be suppressed in the presence of an inhibitor of ubiquitin-proteasome pathway, MG-132, suggesting that the ubiquitin-proteasome pathway is involved in the hypoxia-induced breakdown of BRB. Less